As a poem this is excellent, I really like this, and I can actually sort of see what you mean by this. There are many sorts of love, though, I belive.
Love can be grand, with the butterflies in the stomach, with the romance and the beauty. At least, I want to believe that love like that really exists, and that it's actually lasting. I've only been in love once, but it wasn't like that for me at all. Love isn't always easy. And I can completely understand why you'd compare love to a dark cell.